Great post and it's really what I'm all about. I, too, do all the above. You have to be a good sight reader to do things for community theater, especially the auditions where you might have less than 5 minutes to work up a section of a song with a singer you just met and hands you the music. You also need to be able to read chord charts, standard and Nashville, and lead sheets as well.
For our production of "Thoroughly Modern Millie" that we are in the middle of, I am using the Conductor/piano score which has piano but also the other orchestra parts here and there. I'm playing second keyboard so I'll be covering clarinets, saxes and occasional french horn, celesta and harp, where needed. That is all strictly reading but I think of some of it in terms of chords rather than written notes. On some of that theater music stuff where it changes keys so often, I have to stop and pencil in chord changes over then music because of accidentals and double sharps, etc.
As a last note, just wanted to remind everyone that I do and TEACH all three, have a music school and can teach online, so if anyone is interested in learning more skills in ear training, theory, chords, reading musis, or just about anything else, give me a shout. I would be happy to give anyone a free online consultation.
Jeff
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